What Is Dielectric Fluid? Where Is It Used?

What Is Dielectric Fluid?

Dielectric fluid is an electrically non-conductive liquid with very high resistance to electrical breakdown, even at high voltages.

What Does Dielectric Fluid Do?

Electrical components are often immersed in, or sprayed with, a liquid to remove excess heat. A liquid’s thermal conductivity and specific heat capacity are higher than air’s, which makes the process more efficient at removing waste heat to cool high-power electronics. In other words, dielectric fluid does not conduct electricity, but it does conduct heat. This means it can be used for cooling purposes in certain electrically powered systems.

The main purpose of using dielectric fluid is to quickly prevent and suppress electrical discharges, and traditionally, dielectric fluids have been used to cool transformers, capacitors, high-voltage cables, and switching equipment, to provide electrical insulation, and to suppress unwanted electrical discharge.

Insulating Function

Dielectric fluid provides the electrical insulation needed for controlled spark formation between the electrode and the workpiece.

Cooling Function

The fluid quickly dissipates the high heat generated during spark erosion, protecting both the electrode and the workpiece.

Particle Removal

Dielectric fluid carries away the molten metal particles produced during the process, out of the machining area.

Where Is Dielectric Fluid Used?

In electric vehicles, dielectric fluids can be used to cool the battery, electric motor, power electronics, and electric transmissions. To help with efficient heat transfer and pumping efficiency, the fluids need high thermal conductivity and low viscosity (viscosity: resistance to flow).

Dielectric fluids can be used as capacitors in electrical circuits and can help store electrical energy. They can also be used as an insulating material that can conduct electrical energy while blocking the propagation of electromagnetic waves. Dielectric fluids are generally used to increase the safety of electrical and electronic equipment through insulation.

what is dielectric fluid. where is dielectric fluid used

In electrical discharge machining, because of these beneficial properties, the workpiece is kept submerged in dielectric fluid. As the dielectric fluid, mineral oils or synthetic hydrocarbons are used, and in the field of electrical discharge machining, deionized (desalted) water is also used.

What Does Dielectric Fluid Do in Electrical Discharge Machining?

In electrical discharge machines, dielectric fluid performs three main functions:

It protects the area where material is being removed from air currents and keeps the flow rate of the electrical spark discharge constant.
It performs a cooling function and removes the small chips produced from the workpiece.
It acts as a carrier, moving the chips away from the workpiece to the settling tank.

In electrical discharge machining, vigorous circulation, proper filtering, and periodic renewal of the dielectric fluid are necessary.

Due to the fumes produced and the fragmented, crumbled byproducts, extraction (aspirator) equipment must be present, and fire-safety regulations must be strictly followed.

dielectric fluid in electrical discharge machining — wire EDM

electrical discharge machining working principle and dielectric fluid — Sinker (plunge) EDM

Properties Required in Dielectric Fluids

This raises the question: what should the properties of a good dielectric fluid be?

For effective direct-immersion cooling, a dielectric fluid needs high density, high thermal conductivity, high specific heat capacity, and low viscosity.

The properties expected of a good dielectric fluid are as follows:

Good electrical properties – the fluid should have limited electrical conductivity to prevent arcing and also have a high breakdown voltage
Good material compatibility – the fluid should not damage the elastomer seals, copper, insulation materials, or any other material found in the cooling system.
Low volatility – lower volatility reduces evaporation losses, reducing the need to top off the fluid
High flash point – increases fluid safety and reduces fire risks under high-temperature conditions
Low pour point – the fluid should not freeze or become too viscous to pump at low temperatures
High oxidation stability – the fluid should remain stable at high temperatures and can be expected to perform throughout the vehicle’s service life